APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session T12: Invited Session: Functional Dynamics of Proteins from Physics to Biology
11:15 AM–2:15 PM,
Thursday, March 6, 2014
Room: 205
Sponsoring
Unit:
DBIO
Chair: Xiang-Qiang Chu, Wayne State University, and Michael Brown, University of Arizona
Abstract ID: BAPS.2014.MAR.T12.5
Abstract: T12.00005 : Pulse Dipolar ESR and Protein Superstructures and Function
1:39 PM–2:15 PM
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Abstract
Author:
Jack Freed
(Cornell University)
Pulse dipolar electron-spin resonance (PDS-ESR) has emerged as a powerful
methodology for the study of protein structure and function. This
technology, in the form of double quantum coherence (DQC) -- ESR and
double-electron-electron resonance (DEER) in conjunction with site-directed
spin-labeling will be described. It enables the measurement of distances and
their distributions in the range of 1-9 nm between pairs of spins labeled at
two sites in the protein. Many biological objects can be studied: soluble
and membrane proteins, protein complexes, etc. Many sample morphologies are
possible: uniform, heterogeneous, etc. thereby permitting a variety of
sample types: solutions, liposomes, micelles, bicelles. Concentrations from
micromolar to tens of millimolar are amenable, requiring only small amounts
of biomolecules. The distances are quite accurate, so a relatively small
number of them are sufficient to reveal structures and functional details.
Several examples will be shown. The first is defining the protein complexes
that mediate bacterial chemotaxis, which is the process whereby cells
modulate their flagella-driven motility in response to environmental cues.
It relies on a complex sensory apparatus composed of transmembrane
receptors, histidine kinases, and coupling proteins. PDS-based models have
captured key architectural features of the receptor kinase arrays and the
flagellar motor, and their changes in conformation and dynamics that
accompany kinase activation and motor switching. Another example will be
determining the conformational states and cycling of a membrane transporter,
GltPh, which is a homotrimer, in its apo, substrate-bound, and
inhibitor-bound, states in membrane vesicles providing insight into its
energetics. In a third example the structureless (in solution) proteins
alpha-synuclein and tau, which are important in Parkinson's disease and in
neurodegeneration will be described and the structures they take on in
contact with membranes will be described. Another important development is
that of extending ESR to much higher frequencies (ca. 250 GHz), which has
enabled a multi-frequency ESR approach to the study of protein dynamics that
enables the separation of their complex modes of motion in terms of their
different time scales.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.T12.5